(1) Field of the Invention
This invention relates to dragline buckets and more particularly relates to a removable pipe arch for dragline buckets.
(2) History of the Prior Art
A dragline is an excavating machine which includes a bucket connected with hoist, drag, and dump lines and drawn toward the machine in an excavating step during which the bucket is filled with the material being excavated. Dragline buckets are capable of operating with a predetermined gross suspended load which consists of hardware comprising the bucket structure, the various support and operating lines, and related apparatus, and the payload of material being removed. Any weight which can be eliminated from the hardware may be added to the payload without affecting the gross suspended load being handled by the dragline. Conventional dragline buckets, as illustrated in FIGS. 1 and 2 of the drawings, include a somewhat massive box shaped full clearance arch connected over and between opposite sides of the front of the bucket serving as both a brace and to attach dump ropes to the bucket. The full clearance arch adds substantial weight to the bucket as well as providing unobstructed entry of material into the bucket as the bucket is dragged toward the dragline machine.
One alternative prior art bucket design which reduces the significant weight of the full clearance type bucket arch is the fixed straight through pipe arch illustrated in FIG. 3. While the pipe arch design reduces the hardware weight and significantly increases the payload which can be handled by the bucket, the free flow of material into and out of the bucket is more restricted than with the full clearance arch. In overburden stripping applications having poorly fragmented, large, blocky material, the fixed straight through pipe arch style bucket is often not a feasible means of minimizing bucket weight to increase the effective payload of the bucket. Due to the location and the smaller size of the pipe arch relative to the full clearance arch, the pipe arch is extremely susceptible to damage from material entering or exiting the bucket. The net dragline production increases effected through greater payloads using a pipe arch bucket are often lost due to machine downtime for repairing or replacing damaged arches.
The weight reducing advantages of the pipe arch type dragline bucket are inherent in the present invention with the further advantage of reduced downtime for repairing or replacing the pipe arch.